TT-13185, fixed lines lost in merge conflicts (#6681)

### **User description**
<details open>
<summary><a href="https://tyktech.atlassian.net/browse/TT-13185"
title="TT-13185" target="_blank">TT-13185</a></summary>
  <br />
  <table>
    <tr>
      <th>Summary</th>
<td>Implement OAuth 2.0 Password Flow for API Gateway Authentication
with Upstream Server</td>
    </tr>
    <tr>
      <th>Type</th>
      <td>
<img alt="Story"
src="https://tyktech.atlassian.net/rest/api/2/universal_avatar/view/type/issuetype/avatar/10315?size=medium"
/>
        Story
      </td>
    </tr>
    <tr>
      <th>Status</th>
      <td>Ready for Testing</td>
    </tr>
    <tr>
      <th>Points</th>
      <td>N/A</td>
    </tr>
    <tr>
      <th>Labels</th>
<td><a
href="https://tyktech.atlassian.net/issues?jql=project%20%3D%20TT%20AND%20labels%20%3D%20QA_Fail%20ORDER%20BY%20created%20DESC"
title="QA_Fail">QA_Fail</a></td>
    </tr>
  </table>
</details>
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---

<!-- Provide a general summary of your changes in the Title above -->

## Description

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## Related Issue

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issue first. -->
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to reproduce. -->
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JIRA ticket. -->

## Motivation and Context

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## How This Has Been Tested

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etc. -->
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## Screenshots (if appropriate)

## Types of changes

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the boxes that apply: -->

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Refactoring or add test (improvements in base code or adds test
coverage to functionality)

## Checklist

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that apply -->
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checked. -->
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- [ ] I ensured that the documentation is up to date
- [ ] I explained why this PR updates go.mod in detail with reasoning
why it's required
- [ ] I would like a code coverage CI quality gate exception and have
explained why


___

### **PR Type**
enhancement, bug fix


___

### **Description**
- Enhanced the `Fill` and `ExtractTo` methods for `ClientCredentials`
and `PasswordAuthentication` to handle `ExtraMetadata`, `ClientID`, and
`ClientSecret` fields.
- Updated test assertions in `oas_test.go` by removing lines related to
`ExtraMetadata`.
- Fixed lines lost in merge conflicts related to OAuth 2.0 Password Flow
implementation.



___



PRDescriptionHeader.CHANGES_WALKTHROUGH
<table><thead><tr><th></th><th align="left">Relevant
files</th></tr></thead><tbody><tr><td><strong>Tests</strong></td><td><table>
<tr>
  <td>
    <details>
<summary><strong>oas_test.go</strong><dd><code>Update test assertions by
removing `ExtraMetadata` lines</code>&nbsp; </dd></summary>
<hr>

apidef/oas/oas_test.go

- Removed lines related to `ExtraMetadata` in test assertions.



</details>


  </td>
<td><a
href="https://github.com/TykTechnologies/tyk/pull/6681/files#diff-74029ee88132d30d6478c96a35f8bb2200e0c8e6f42f2c9b147dc6bb7ce74644">+0/-2</a>&nbsp;
&nbsp; &nbsp; </td>

</tr>                    
</table></td></tr><tr><td><strong>Enhancement</strong></td><td><table>
<tr>
  <td>
    <details>
<summary><strong>upstream.go</strong><dd><code>Enhance OAuth handling
with `ExtraMetadata` and credentials</code></dd></summary>
<hr>

apidef/oas/upstream.go

<li>Added <code>ExtraMetadata</code> field handling in <code>Fill</code>
and <code>ExtractTo</code> methods for
<br><code>ClientCredentials</code>.<br> <li> Added <code>ClientID</code>
and <code>ClientSecret</code> field handling in <code>Fill</code> and
<code>ExtractTo</code> <br>methods for
<code>PasswordAuthentication</code>.<br>


</details>


  </td>
<td><a
href="https://github.com/TykTechnologies/tyk/pull/6681/files#diff-7b0941c7f37fe5a2a23047e0822a65519ca11c371660f36555b59a60f000e3f4">+8/-0</a>&nbsp;
&nbsp; &nbsp; </td>

</tr>                    
</table></td></tr></tr></tbody></table>

___

> 💡 **PR-Agent usage**: Comment `/help "your question"` on any pull
request to receive relevant information

apidef/oas/oas_test.go

@@ -313,10 +313,8 @@ func TestOAS_ExtractTo_ResetAPIDefinition(t *testing.T) {
 		"APIDefinition.AnalyticsPlugin.PluginPath",
 		"APIDefinition.AnalyticsPlugin.FuncName",
 		"APIDefinition.UpstreamAuth.OAuth.ClientCredentials.Enabled",
-		"APIDefinition.UpstreamAuth.OAuth.ClientCredentials.ExtraMetadata[0]",
 		"APIDefinition.UpstreamAuth.OAuth.PasswordAuthentication.Header.Enabled",
 		"APIDefinition.UpstreamAuth.OAuth.PasswordAuthentication.Header.Name",
-		"APIDefinition.UpstreamAuth.OAuth.PasswordAuthentication.ExtraMetadata[0]",
 	}
 
 	assert.Equal(t, expectedFields, noOASSupportFields)

apidef/oas/upstream.go

@@ -706,6 +706,7 @@ func (c *ClientCredentials) Fill(api apidef.ClientCredentials) {
 	c.ClientSecret = api.ClientSecret
 	c.TokenURL = api.TokenURL
 	c.Scopes = api.Scopes
+	c.ExtraMetadata = api.ExtraMetadata
 
 	if c.Header == nil {
 		c.Header = &AuthSource{}
@@ -717,10 +718,13 @@ func (c *ClientCredentials) Fill(api apidef.ClientCredentials) {
 }
 
 func (p *PasswordAuthentication) Fill(api apidef.PasswordAuthentication) {
+	p.ClientID = api.ClientID
+	p.ClientSecret = api.ClientSecret
 	p.Username = api.Username
 	p.Password = api.Password
 	p.TokenURL = api.TokenURL
 	p.Scopes = api.Scopes
+	p.ExtraMetadata = api.ExtraMetadata
 	if p.Header == nil {
 		p.Header = &AuthSource{}
 	}
@@ -756,6 +760,7 @@ func (c *ClientCredentials) ExtractTo(api *apidef.ClientCredentials) {
 	api.ClientSecret = c.ClientSecret
 	api.TokenURL = c.TokenURL
 	api.Scopes = c.Scopes
+	api.ExtraMetadata = c.ExtraMetadata
 
 	if c.Header == nil {
 		c.Header = &AuthSource{}
@@ -767,10 +772,13 @@ func (c *ClientCredentials) ExtractTo(api *apidef.ClientCredentials) {
 }
 
 func (p *PasswordAuthentication) ExtractTo(api *apidef.PasswordAuthentication) {
+	api.ClientID = p.ClientID
+	api.ClientSecret = p.ClientSecret
 	api.Username = p.Username
 	api.Password = p.Password
 	api.TokenURL = p.TokenURL
 	api.Scopes = p.Scopes
+	api.ExtraMetadata = p.ExtraMetadata
 }
 
 func (u *UpstreamOAuth) ExtractTo(api *apidef.UpstreamOAuth) {